This is my new main weapon for Samurai. The additional effect is somewhat like applying Threnody on, to the extent that skillchains seem to be resisted less often. I would also like to think that the blind/silence/paralyze effects of Samurai weaponskills land more easily as well.
Good in its own right, but for SAM your looking at more damage. Which means Hagun will still win
Yukikaze > Gekko = Fragmentation
The difference in damage between the yukikaze and gekko will be made up in the fragmentation skillchain with maybe even extra damage. So the magic evasion down will be good yes, but the overall skillchain damage will be low due to not putting out the right numbers with a weaponskill like the hagun would. Nice augment none the less